title: Variation in astigmatism following the single-step, self-sealing clear corneal section for phacoemulsification.
abstract: OBJECTIVE
  A single-step, self-sealing, 3.2 mm clear corneal section is described and the incidence and variation of surgically induced astigmatism following phacoemulsification over a period of 3 months is determined.
  
  
  METHODS
  Twenty-two patients who underwent uncomplicated 3.2 mm clear corneal phacoemulsification with foldable Allergan silicone intraocular lens implantation were autorefracted pre-operatively and on day 1, week 1, week 6 and at 3 months. The variation in induced astigmatism was analysed using the subtraction method and vector analysis. The change in direction of the cylindrical axis was examined.
  
  
  RESULTS
  The induced astigmatism represented by the total vector on day 1 was 1.17 D and vector decomposition ratio, ATR:WTR (against-the-rule:with-the-rule), was 21.05:78.95. The total vector increased by 0.5 D in the first week and then stabilised. Vector decomposition showed an against-the-rule astigmatic drift so that by 3 months the ATR:WTR was 40.49:59.91. There was a tendency of the axis of the negative cylinder to swing towards the corneal section meridian on day 1 and to oscillate around that meridian at week 1 and week 6. By 3 months the direction reverted to that pre-operatively, in most cases.
  
  
  CONCLUSIONS
  The single-step, self-sealing clear corneal section is mechanically stable and, though there is some variability in the measured astigmatism, there is an acceptable functional result throughout the post-operative period.
authors.affiliation: Department of Ophthalmology, Charing Cross Hospital, London, UK.
authors.forename: S
authors.initials: S
authors.lastname: Rauz
authors.forename: A
authors.initials: A
authors.lastname: Reynolds
authors.forename: H W
authors.initials: HW
authors.lastname: Henderson
authors.forename: N
authors.initials: N
authors.lastname: Joshi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000209:etiology* / Q000503:physiopathology; D003315:Cornea / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D019654:Lens Implantation, Intraocular / Q000379:methods; D008297:Male; D008875:Middle Aged; D018918:Phacoemulsification / Q000009:adverse effects*; D011184:Postoperative Period; D014792:Visual Acuity